This invention relates to thermoplastic polymer materials for the preparation of three-dimensional prototypes or models. Prototypes of parts are made and used in testing in a wide-variety of industries, such as the automobile, aerospace, and biomedical prostheses manufacturing industries. After successful testing the prototypes of parts, a mold of the prototype can be made and the part can be manufactured on a mass production basis.
There are three ways of making prototypes. One method involves simply making a mold of the part, making the prototype, and then testing the prototype. However, this method requires the cost of making a mold, which itself can be extremely expensive and time-consuming. Moreover, this method may require numerous molds to be made on a trial and error basis until a successful part has been designed that sufficiently passes the required testing.
A second method of making prototypes involves sculpting a three-dimensional prototype of a particular shape from a block work piece. In this method, the prototype is drawn either manually or using computer-aided design (CAD) techniques, and the prototype is formed by removing material from a block work piece. The part can be further machined either manually or using computer-aided machining (CAM) techniques. However, this method can also be a costly and time-consuming process because it may require repeated iterations until a desired prototype is made.
A third method that has been developed involves the formation of a three-dimensional prototype by depositing multiple layers of a material in a fluid state onto a base. The fluid solidifies to define the prototype element. In general this method is often termed freeforming in the prior art. For example, such a method is taught in U.S. Pat. No. 5,340,433, and U.S. Pat. No. 5,121,329, both issued to S. Scott Crump and assigned to Stratasys, Inc. incorporated herewith by reference. In this method, a layer of the fluid material solidifies and then another layer of fluid material is deposited over the preceding layer. The thickness of each layer is controlled by the distance between the tip of the dispensing head and the preceding layer. However, there are a number of disadvantages to the method and apparatus taught in this third method because only certain types of materials can be suitably used to make the prototypes, such as waxes having low melt viscosity and strength. Thermoset materials may be used to try to improve strength and toughness. In any event, this prior art deposition method may not produce durable prototypes made from high performance engineering polymers and composites.
There is a clear need for a method and apparatus that can make stronger and tougher prototypes made of engineering polymers and composites having high melt viscosity and long chain lengths. Such a method and apparatus is disclosed in U.S. Ser. No. 08/825,893, filed Apr. 2, 1997, which is incorporated herein by reference.
As noted in U.S. Ser. No. 08/825,893, materials for high pressure fused deposition include polyaryletherketone (PEEK.RTM. produced by Victrex), polmethylmethacrylate (PMMA.RTM. produced by DuPont), polycarbonate (Lexan.RTM. made by General Electric Plastics), thermoplastic polyurethane (Pellethane.RTM. made by Dow Chemical), and polylatic acid/polyglycolic acid block copolymer (a bio-absorbable material made by a Biomet joint venture). Fused deposition of fiber reinforced grades of engineering polymers and composites, for example PEEK.RTM. and Lexan.RTM. can also be used for the invention disclosed in U.S. Ser. No. 08/825,893. Moreover, prototypes can be made in accordance with that invention using fiber reinforcement. For example, carbon fiber reinforced PEEK.RTM. materials had a tensile strength of over 36000 psi exhibited a very high fracture toughness and demonstrated highly anisotropic mechanical properties whereas unreinforced materials did not.
Thus, there is a clear need for strong materials that can be used in a method for making prototypes, and in particular materials for the method involving the depositing of multiple layers in a fluid state onto a base. More specifically, there is a need for strong thermoplastic polymers that can be easily melt extruded by an extrusion freeforming apparatus in layer form, and which then solidify upon cooling so that complicated shaped parts can be freeform fabricated by precisely and sequentially depositing polymer layers upon one another until the desired component is produced. There is also a need for strong materials that can be used as a support material for use in an extrusion freeforming apparatus that prevents the sagging of deposited molten, prototype material layers before cooling and solidification. Support materials are particularly important when fabricating complex geometry, dimensionally accurate prototypes having numerous overhangs, or internal cavity features.